Study guide
2.3 Biomechanics, Levers, Force, Torque, and Planes of Motion
NASM Certified Personal Trainer Study Guide Exam
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1 1. Orientation, Official Sources, and Exam Strategy
1.1 What the NASM-CPT Credential Tests 1.2 Eligibility, Scheduling, PSI, and Exam-Day Rules 1.3 Blueprint Weights and How to Allocate Study Time 1.4 The OPT Model as the Organizing Map 1.5 How to Use ExamFinch Practice Questions 1.6 12-Week Study Plan and Readiness Metrics
2 2. Basic Sciences: Anatomy, Physiology, and Biomechanics
2.1 Nervous, Muscular, Skeletal, Cardiorespiratory, and Endocrine Systems 2.2 Bones, Joints, Muscle Actions, and Functional Anatomy 2.3 Biomechanics, Levers, Force, Torque, and Planes of Motion 2.4 Muscle Action Spectrum and Kinetic Chain Relationships 2.5 Length-Tension, Force-Couple, Reciprocal Inhibition, and Autogenic Inhibition 2.6 Motor Learning, Motor Control, and Movement Quality
3 Chapter 3: Nutrition, Energy Systems, and Weight Management
3.1 Macronutrients, Micronutrients, and Hydration Within CPT Scope 3.2 ATP-PC, Glycolytic, and Oxidative Energy Systems 3.3 EPOC, Caloric Balance, and Units of Energy 3.4 Dietary Reference Intakes, Portion Size, Meal Timing, and Nutrient Density 3.5 Supplements, Labels, Fad Diets, and Scope Boundaries 3.6 Weight-Management Factors and Referral Decisions
4 Chapter 4: Client Relations, Behavior Change, and Coaching
4.1 Rapport, Active Listening, and Client-Trainer Relationship 4.2 SMART Goals, Outcome Goals, Process Goals, and Expectation Management 4.3 Stages of Change and Readiness Conversations 4.4 Motivational Coaching, Reinforcement, and Habit Strategy 4.5 Barriers, Social Support, Environment, Stress, and Time 4.6 Psychological Responses to Exercise and Adherence
5 Assessment, Intake, Risk, and Physiological Testing
5.1 PAR-Q, Health History, Lifestyle Questionnaire, and Documentation 5.2 Medical Risk Factors, Red Flags, and Referral 5.3 Resting Heart Rate, Blood Pressure, BMI, and Waist-to-Hip Ratio 5.4 Cardiorespiratory Assessments: Step Test, Rockport, VO2max, and RPE 5.5 Body Composition, Circumference, Skinfold, and BIA 5.6 Reassessment Timing and Outcome Tracking
6 Movement Assessment, Posture, and Kinetic Chain
6.1 Kinetic Chain Checkpoints 6.2 Static Postural Assessment 6.3 Overhead Squat Assessment 6.4 Single-Leg Squat, Push, Pull, and Gait Assessments 6.5 Strength, Endurance, Power, and SAQ Assessments 6.6 Turning Assessment Findings Into First Program Decisions
7 Chapter 7: OPT Model and Program Design Framework
7.1 OPT Levels and Phases 7.2 Stabilization Endurance 7.3 Strength Endurance, Hypertrophy, and Maximal Strength 7.4 Power Training 7.5 Periodization, Specificity, Variation, Overload, and GAS 7.6 Acute Variables and Program-Design Math
8 Chapter 8: Training Modalities: Cardio, Flexibility, Core, Balance, Reactive, and SAQ
8.1 Flexibility Continuum: SMR, Static, Active-Isolated, and Dynamic 8.2 Cardiorespiratory FITTE, Stage Training, Intervals, and Steady State 8.3 Core Stabilization, Strength, and Power 8.4 Balance Stabilization, Strength, and Power 8.5 Reactive/Plyometric Training Progressions 8.6 SAQ, Resistance Systems, Modalities, and Technology
9 Chapter 9: Exercise Technique, Cueing, and Safe Instruction
9.1 Session Setup, Warm-Up, and Cool-Down 9.2 Flexibility, Core, Balance, Reactive, and Resistance Technique 9.3 Cueing: Kinesthetic, Auditory, and Visual 9.4 Progressions, Regressions, and Exercise Modification 9.5 Spotting, Breathing, and Safe Training Environment 9.6 Stop, Modify, or Refer: Signs and Symptoms During Training
10 Chapter 10: Special Populations and Program Modification
10.1 Youth Training 10.2 Seniors and Active Aging 10.3 Prenatal and Postnatal Considerations 10.4 Obesity and Weight-Management Clients 10.5 Clinical Clients, Hypertension, Diabetes, and Cardiometabolic Risk 10.6 Exercise Selection, Contraindications, and Referral
11 Professional Responsibility, Scope, Business, and Emergencies
11.1 NASM Scope of Practice 11.2 Ethics, Documentation, Records, Appearance, and Punctuality 11.3 Safety, Equipment Maintenance, and Facility Risk 11.4 Emergency Action Plans, EMS Activation, and Incident Response 11.5 Business Development, Marketing, Sales, Retention, and Ascension 11.6 Continuing Education, Recertification, and Credible Resources
12 Integrated Scenarios, Final Review, and Career Launch
12.1 Assessment-to-Program Scenario Lab 12.2 Behavior-Coaching Scenario Lab 12.3 Exercise Technique and Safety Scenario Lab 12.4 Full-Domain Final Review Plan 12.5 Test-Day Pacing and Retake Strategy 12.6 First 30 Days After Passing NASM-CPT
2.3 Biomechanics, Levers, Force, Torque, and Planes of Motion
Key Takeaways Explain This Topic AI
The three planes of motion — sagittal, frontal, and transverse — organize every movement and every exercise a trainer programs.
Force is a push or pull (mass times acceleration); torque is a rotational force equal to force times the moment arm, which is why load position changes difficulty.
The body uses three lever classes, and third-class levers (effort between fulcrum and load) are by far the most common, favoring speed and range over mechanical advantage.
Moving a load farther from the working joint lengthens the moment arm and increases torque even when the external weight is unchanged.
Newton's laws — inertia, acceleration, and action-reaction — underlie how trainers manipulate tempo, load, and stability.
Last updated: June 2026
The Three Planes of Motion
All human movement is described relative to three imaginary planes of motion , each bisecting the body and each paired with an axis of rotation. Mastering them lets a trainer classify any exercise and program balanced, multiplanar training.
- Plane Divides body into Axis Primary movements
- Sagittal Left and right halves Medial-lateral Flexion, extension, dorsiflexion, plantarflexion
Frontal Front (anterior) and back (posterior) Anterior-posterior Abduction, adduction, lateral flexion, eversion/inversion
Transverse Top (superior) and bottom (inferior) Longitudinal (vertical) Internal/external rotation, horizontal abduction/adduction, supination/pronation
Most foundational gym movements are sagittal-plane (squats, presses, curls, lunges, running). The frontal plane adds side-to-side work (lateral lunges, lateral raises), and the transverse plane adds rotation (cable chops, throwing). Because daily life and sport are multiplanar, NASM emphasizes progressing clients beyond the sagittal plane once they demonstrate control.
Force, Torque, and the Moment Arm
Force is any push or pull acting on the body, defined by Newton's second law as force = mass × acceleration . In training, external force comes from gravity acting on a load, bands, machines, or the client's own bodyweight.
Torque is rotational force — the turning effect produced when a force acts at a distance from a joint's axis. It equals force × moment arm , where the moment arm is the perpendicular distance from the axis of rotation to the line of force. This single relationship explains many exam scenarios: holding a dumbbell with the elbow extended (long moment arm) creates far more torque at the shoulder than holding the same dumbbell close to the body (short moment arm), even though the weight never changed.
Practical applications:
Sliding the hands wider on a lat pulldown or moving a plate farther from the trunk during a core exercise increases torque and difficulty.
Keeping the bar path close to the body in a deadlift shortens the moment arm at the spine, reducing the rotational load and protecting the low back.
Lever Systems in the Body
A lever is a rigid bar (a bone) that rotates around a fulcrum (a joint) when force is applied against a resistance. The three classes are defined by the order of the fulcrum, effort, and load:
- Lever class Arrangement Body example
- First-class Fulcrum between effort and load Nodding the head (atlanto-occipital joint)
- Second-class Load between fulcrum and effort Standing calf raise (rising onto the toes)
- Third-class Effort between fulcrum and load Biceps curl at the elbow
The third-class lever is the most common arrangement in the human body. It sacrifices mechanical advantage — the muscle must produce more force than the load — but rewards the body with greater speed and range of motion at the end of the limb. This is a frequent exam fact: when asked which lever dominates human movement, the answer is third-class.
Newton's Laws Applied to Coaching
Three of Newton's laws turn biomechanics into coaching cues:
Law of inertia (first law): a body at rest or in motion stays that way unless acted on by a force. Heavier loads have more inertia, so a slow, controlled start prevents momentum from taking over.
Law of acceleration (second law): force equals mass times acceleration. To accelerate a load faster (power training), the client must apply more force.
Law of reaction (third law): for every action there is an equal and opposite reaction. Pushing into the ground during a jump produces an equal ground-reaction force that propels the body upward.
Trainers use these principles to adjust tempo, load placement, and stability. Slowing the eccentric tempo increases time under tension; lengthening a moment arm raises torque; and changing the base of support alters how ground-reaction forces are managed. Recognizing why an exercise becomes more demanding — rather than only that it does — is the reasoning NASM biomechanics questions assess.
Putting Biomechanics to Work in Program Design
Biomechanics is not abstract physics — it is the toolkit a trainer uses to make an exercise easier, harder, or more specific without ever changing the weight on the bar. Several worked applications the exam expects:
Regressing or progressing by leverage: a plank held from the knees shortens the lever between the fulcrum (shoulders) and the load (hips), reducing torque on the core; moving to a full plank lengthens that lever and raises the demand.
Changing the plane to add specificity: an athlete who cuts and rotates in sport needs transverse-plane training (cable rotations, rotational med-ball throws), not just sagittal-plane squats and presses.
Managing spinal torque: coaching a lifter to keep the load close to the body during a row or deadlift shortens the moment arm at the lumbar spine, lowering the rotational stress that drives low-back strain.
Using ground-reaction force for power: plyometric and jump training teach the client to apply force rapidly into the ground so the equal-and-opposite reaction propels the body, the basis of NASM's power phase.
Stability and the Base of Support
A wider base of support and a lower center of gravity make a position more stable, which is why NASM often begins clients on stable surfaces and two-leg stances before progressing to single-leg or unstable-surface work. Narrowing the base or raising the center of gravity increases the balance demand and forces the nervous system and stabilizers to work harder. Each of these adjustments is a deliberate biomechanical choice, and the exam rewards the trainer who can explain the underlying reason — leverage, plane, force, or stability — rather than guessing.